Cathode-ray-oscillograph



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M. KNQLL Er AL CATHODE RAY OSCILLOGRAPH Filed NOV. 18, 1929 ssheets-sheet 2 Patented Apr. 7, 1936 UNITED STATES'CATHODE-RAY-OSCILLOGRAPH Max Knoll, Berlin-Lichterfelde, Ludwig Schiff,

Berlin, and Carl Stoerk, Berlin-Neukolln, Germany; said Stoerk assignorto said -Knoll and said Schiil' Application November 18, 1929, SerialNo. 408,006 In Germany December 12, 1928 14 Claims. (C1. Z50-27.5)

'I'his invention relates to cathode-ray oscillographs. We may explain ingeneral what cathode-ray cscillograph is.

A beam of electrons ejected from the cathode of a vacuum tube can, byvarious known methods (e. g. curvature of cathode surface, magneticfields, or by ionic methods) be made to converge lnto a focus. The beamcan also, by means of the effect exercised by electrostatic or mag- :unetic elds, be deflected in a direction perpendicular to the line of itspath, and the focal point be made to describe a corresponding path on asurface perpendicular to the beam.

The electrons being without mass, and there l5 being no inertia to beovercome in their deflection, the velocity at which their deflection cantake place, and consequently the recording-speed of 'the focal point, ispractically unlimited.

On the other hand, owing to the fact that the 20 entire rays of a beamof cathode-rays are united in the focal point, the effect produced issufcient, however extraordinarily high the recordingvelocity of thefocal point, for instance to render the path of the point visible, tofix it photographi- 25 cally, or, by means of the charge conveyed by theelectrons, to cause rushes of current, and so on.

The tubes which serve thus for the production of cathode-rays, forfocussing them at a point, for moving the point, and for controlling themovement of the point, are termed cathode-ray oscillographs.

Cathode-ray oscillographs have found most varied and fruitfulapplication not only for scientie, but also for practical purposes. 'Iheeffect :i5 of the cathode rays produced along the path of their focuscan be utilized in various Ways. For instance, the energy of the raysmay be transmuted partly into light-energy on a continuous fluorescentsurface, and their path be thus made l.) directly visible to the eye;the path may be recorded upon a sensitive strip-surface; or the electriccharge conveyed by the ray electrons may be transferred to a number ofelectrodes scattered over the Writing-surface and the rushes of currentthereby produced further utilized. Mutually independent relays may beset in action, for example, or the rushes of current be passed throughphoto-electric cells whose resistance varies according to exposure.

'I'he following are a few of the applications feasible, which will givesome idea of the great technical significance of the oscillograph, andof the number and variety of the domains in which it may be successfullyturned to account.

In the case of electric overhead transmissionlines, the oscillograph isthe only kind practicable for investigating the influences exercised byatmospheric electricity e. g. lightning discharges, or the surges ofcurrent caused in such systems by suddenly switching on or off thecurrent, which, though usually they last only from one-hundredthousandthto one-millionth of a second, often destroy transformers, switches, andcables. By moans of oscillogram records it is possible to ascertain withthe utmost exactness the moment when the surge of current occurred, itscourse and its amplitude. On the basis of the observations made,measures may be taken to prevent damage tothe plant. If the records areregistered on a constantly moving strip of film, no attendance of theapparatus is needed, and any perturbances are recorded automatically asthey occur. It is also possible, by the generation of travelling waves,to observe separately the behaviour, during the extraordinarily shortperiod of duration of the surge, of each single piece of apparatuscomposing the plant, such as transformers, switches, insulators, etc.,and thus to gather valuable data for the proper construction of suchapparatus.

If when periodical oscillations of the focus of the electronic beam areproduced by an electric or magnetic field of definite frequency, anumber of electrodes are arranged in the path described by the focalpoint, and connected with a conducting Wire serving to draw off thecharge carried by the electrons, a corresponding higher frequency is setup in that conducting wire. 'I'he cathode-ray oscillograph can thus beutilized as a frequency converter.

The extraordinary facility with which the focal point may be guided andcontrolled, enabling it to describe quite easily, for instance, inonethousandth of a second, upon a surface 6 x 6 cm, a narrow zigzag 36meters in length, correspond-A ing to a recording velocity of 36kilometers per second, and further the possibility, even at nthisenormous speed, of obtaining the above-mentioned chemical and physicaleffects, render the cathode-ray oscillograph especially suitable for usefor picture-telelgraphy and television, and equally well either fortransmission or reception.

With cathode-ray cscillographs as hitherto employed it has beenconsidered an essential requisite to let the focus work in a Vacuumtube.

This has involved great p-ractical diflculties. If i for instance anoscillogram had to be recorded photographlcally, the photographic plateshad to be introduced into the vacuum and afterwards removed. Not onlywas this operation awkward to perform and accompanied by a loss oftime,l

but the cathode-ray tube had to remain in connection with the air-pump,since it was necessary to destroy the vacuum after, and restore itbefore, every operation. To procure a continuous record, i. e. one ofany considerable duration, upon a lengthy strip of film, was thus inpractice extremely difficult.

These difficulties involved in the working of a ray focus in a vacuumhave probably been the reason why the cathode-ray oscillograph has notbeen employed in the systems of picturetelegraphy and televisionhitherto put into practice, although it would appear to be predestinedas just the device that pioture-telegraphy and television required.

The present invention consists in the fact, that the focus of thecathode-rays is made to work not within the vacuum tube, but outside it.

Means had already been devised for allowing the entire cathode-ray beamor a portion of the same pass through an aperture or egress through awindow in the tube, in order to conduct scientific investigations as tothe nature of electrons, or their physical and chemical influence uponvarious substances, and so on. In both cases however, the electronsexercised their effect only in their natural actual density, not howeverin concentrated form. The quantity of heat given off per unit of surfacewas thus comparatively small. Consequently, with such apparatus,operating as they did only with small electronic densities, the heatgenerated by which being dispersed was easily drawn off, and nodifliculties occurred. At such small electronic densities, thosephysical and chemical effects which due to its power of focusing theray-beam renders the cathode-ray oscillograph especially capable, cannotbe obtained.

With cathode-ray oscillographs the rays assembled at the focal point hadhitherto not been passed through such a window. This-despite the greatand obvious inconveniences involved in working the cathode-ray focusinside the vacuum-is probably due to the following circumstances. On theone hand the window, through which the cathode-rays are to be allowedegress, must be kept extraordinarily minute in width. On the other hand,the path traversed by the cathode-rays outside the window must, owing tothe strong dispersive action which promptly takes place, be of theshortest possible length. This means that the focus mast be movedpractically within the plane of the window itself. The extremely intenseeffect generated by the focus, due to the highly concentrated density ofthe electrons, would thus swift'y burn or melt away and destroy thewindow. This destructive effect can, howeverand herein lies partly thebasis of the invention-be prevented by the velocity of the recordingoperation made possible by the cathode-ray osciilograph, which is such,that no time is allowed at any point for the generation of heat in anyapprecl able quantity.

It is further necessary, and the invention provides for this, to devisemeans to ensure that the focus, after the record has been made, isinstantaneously and automatically diverted from the window.

The thin window, through which the cathoderays find egress, must bereinforced on the inside to enable it to withstand the excess ofpressure from without; In the case of the abovementioned types ofapparatus, for scientific purposes, means had already been devised. ofreinforcing thewindow (the so-called Lenard window), for

instance with a hexagonal grid. In order to prevent this necessaryreinforcement from having a detractive shading effect upon the beam, lt

. cathode-rays is enabled, by the means provided by this invention, towork outside the vacuum tube instead of within it, does away at onestroke with all the above-mentioned inconveniences hitherto imposed bythe necessity of carrying on the operation in the vacuum. The affectingof photographic or fluorescent surfaces, fixed or moving record-strips,fluorescent screens, arrangements of electrodes and the like is vnowaccomplished outside the vacuum in the atmospheric air. The working ofthe various parts of the apparatus, their observation and exchange canall be carried out without difficulty. As the vacuum does not requirerenewal when a record is taken or when a photographic surface isexchanged, the tube from the vacuum pump may in many cases be sealed offfrom the vacuum pump, thus permitting of extensive simplification of thewhole apparatus required.

If the focus of the electronic beam has to affeet a fluorescent layer(for instance, in order to make visible records of oscillograms of rapidsuccession of occurrences or of telephotographs), the uorescent layermay be deposited directly on the narrow Window of egress and renewed asrequired; the luminous oscillogram or picture can be freely observed,without, as was previously the case, any partial absorption of the lightor distortion of the picture being occasioned by the glass of the tube.

As electron-permeable substances the same materials may in general beused as were formerly employed for the Lenard tubes already mentioned.These are, first of all, thin metal foils, e. g. aluminium,chromium-nickel, steel alloys, beryllium. Also foils of insulatingmaterial, celluloid, cellophane, cellulose products, etc. may be used.Porous materials, such as paper, can also be used, the pores of whichare just fine enough to oppose to the passage of gases a relativelyhigh, and to that of electrons a. relatively low, resistance. In thelatter event the slight quantity of gas admitted through the pores mustof course be constantly drawn off by an air-Dump. Owing to theircomparatively low atomic weight, glasses may also be used, especiallysuch with components of particularly low atomic weight, as for examplethe Lindemann glass so often employed for X-ray tubes, consisting ofberyllium, lithium and boron.

In general it will be necessary to reinforce the thin foil required forthe purpose described by a framework to sustain the outer atmosphericpressure. This framework may, for instance, consist of a wire-netting,which may in its turn be reinforced by means of a bearing cross,supporting grid or the like. For the reinforcement of the foil it ispossible also to employ a thin metal plate perforated plentifully withsmall holes. For the making of such a plate, appropriately perforated, anew process had to be devised. The purpose of the framework as employedin the invention is to make it possible to use, for the window, foil ofextremest thinness, in order thereby to insure that the window shall bepermeable to the electrons to a corresponding maximum degree. Further,in the framework, the ra.-

tio of the total area of the perforations or apentures of admission tothe total area of the nonperforated non-permeable portion oftheframework, has to be as great as possible. Further also, the aperturesof admission must lie as densely as possible together and be of suchsmall size, that the focal spot covers simultaneously several adjacentapertures. The making of such plates involves special difficulties. Tomake such perforated plates the present invention employs a processsimilar to that used in autotype printing for the making oi' theprinting-blocks. As is known, it is possible, by means ofstipplingprocess photography, to engrave upon a surface adjacently, atextraordinarily minute intervals, dots of any desired form-square, forinstance, the ratio of the width of the dots to the Width of the linesof the network of clear spaces between the dots depending upon thedegree of illumination oi the photographed surface, It is possible thusto cover a surface with an extremaly dense network of dots of uniformsize. 'Whereas however in the making of a printing-block the network oflines is etched into the block, in making a perforated plate for thepurpose here in View the network of lines is imprinted or copied on tothe plate, and the dot-surfaces etched through the plate. The line-workcan also be engraved into the plate, the lines of engraving covered witha protecting layer, and the dot-surfaces lying between the lines etchedthrough the plate.

The thin foil forming the window can also, instead of being reinforcedsubsequently by the grid, be made directly upon the outer surface of thegrid, For this purpose the holes of the perforated plate forming thegrid can be lled in with a substance which may be later on removed (forinstance, wax, paraffin), and a thin layer, e. g. of beryllium, iron, orsilicium, deposited galvano-vplastically or by cathode-sputtering overthe entire outer surface of the plate. A thin layer of some acid-proofsubstance such as gold for instance can be deposited on the plateprevious to perforation and the holes then etched outl in the manneralready described. In this way are obtained an extraordinarily intimatevacuum-proof connection between foil and grid, perfect reinforcement,and the maximum abduction of heat. The thickness of the foil can bereduced to as little as 1/10,000 mm. So thin a foil would, unless by souniting it with the grid, be extraordinarily diicult, or practicallyimpossible, to mount. Windows made in this way are permeable toelectrons to a degree hitherto never even remotely approachable; theyare, further, owing' to the effective abduction of the heat, not liableto be burnt through; they are easy to make and-to use; and thanks totheir perfectly plane form, enable sharply dened photographs to be takenwith ordinary plates or lms.

The focussing of the electron rays as required for the oscillographaccording to the present 1nvention, can be eiected in the known manner,e. g. by magnetic elds. A new arrangement, especially convenient for thepurpose in view, based on electrostatic effect, consists in fixing, at

'* certain intervals from one another, co-axially with, andsymmetrically to, the electronic beam ejected by the cathode, pairs ofelectrodes of suitable form (e. g. alternately perforated metalcylinders with small, and washers with large, diameter), which areconnected alternately with appropriate voltages. In this way there areproduced divergent electric elds with a stress acting obliquely to thedirection of the beam, in such a way as to compress the beam radially.If

the voltage is sufficiently high, one single pair, of electrodes maysuffice to effect this concentra' tion. The divergent fields can beobtained by various types of electrode. If a controlling voltage issupplied to such a device, the intensity of the electrons in the beam,and thereby the intensity of the focal spot, can be varied withoutinertia. The especial advantages of this arrangement are: ease inconstruction and mounting, small weight, small dimensions, and avoidanceof consumption of current.

In order to obtain a small focus, it is requisite thatthe electron raysbe ejected from as small as possible a surface of the cathode, just asin an optical system the obtaining of a small focus is dependent uponthe diameter of the source cf light. According to the invention, theelectron rays are produced by autoelectronic discharge from a coldcathode in a high vacuum, by an eX traordinarilyhigh strength ofelectrical eld (e. g, one million volt/cm), being produced on thesurface of the cathode. The most simple form oi arrangement of such adischarge-tube consists of a point with a very small radius of curvatureas cathode, with an anode, for instance in the form of ahollow sphere,placed opposite to it at a short distance. Similar arrangements havealready been proposed for X-ray tubes, but owing to the high intensityof current required with the more recent types of X-ray tube, have notyet been applied in practice. For cathode-ray oscillographs, however,the current therewith obtainable (amounting to about 0.001 amp.) isquite adequate. As the electron rays are emitted only from the outer endof the point, which has a diameter actually of only about 0.01 m/m, (i,e. only a triing fraction of those emitting surface which would exist,e. g. in the case of a hotcathode tube), the power of focussing theraybeam owing to such discharge-tubes, is extraordinarily great andincreases the eiiiciency of the cathode-ray oscillograph considerably.With this arrangement the anode must be provided with a co-axial boringfor. the passage of the electrons.

In many cases, e. g. for the photographic record of oscillograms or ofpictures, it is well to be able to observe the path described by thefocus of the electron rays on the window-surface, or to observe theoscillogram or photo itself while it is being recorded, in order tocheck the proper adjustment and functioning of the device. As the outersurface of the window is covered by the photographic plates, or-with acontinuous recordby the photographic lm passing by, or by the shutter,the observation must take place from the inner side. The observation isrendered possible by'the foil being covered on its inner or outer sideor on both sides with just a lm of luminescent layer. The observationcan then take place in a customary manner through a glass side-window inthe tube. If the luminescent layer is applied only on the outer side ofthe foil, the observation can be made through the foil, which, owing toits extreme thlnness is translucent or transparent. In somecircumstances it may also suilce, instead of the foil to cover the gridwith a luminescent substance.

The application of 'a phosphorescent layer,

especially on the outer side of the foil, oil'ers the further advantage,that the photographic eilect is i screens etc. in the evacuated vesselto be shifted and adjusted at will, these parts can be supported bypliable intermediate organs held in position to withstand the outeratmospheric pressure, e. g. elastic spring devices or membrances ofmetal, in such a manner as to allow free sliding or swinging movement.

Special means are provided in order to keep the focus-so long as it isnot moving at its great recording speed-diverted from the Window orother electron beam receiving member. This may be effected in a mannerknown per se, by diverting the electronic rays sideways by means of aconstant magnetic or purely electrical eld or a combination of both.Preferably a plate of beryllium or other substance of low atomic weightmay be arranged, against which the rays strike during their diversion,in order to prevent as much as possible the generation of X-rays. Forthe further protection of the observer and of the photographic layeragainst X-rays this plate is in turn covered with an envelope ofmaterial of high atomic weight, e. g. lead.

According to the invention the protection of the window may be effect-edby intercepting the electron rays instead of diverting them, i. e. byarranging in the path of the electronic rays a bored-through negativelycharged stopping-electrede, the negative charge of which is led off atthe beginning of the recording operation. As the cathode-rayoscillograph which is the subject of the invention is intended to beused for rendering visible or recording extraordinarily rapidlyoocurring phenomena, or for television purposes, the switching on or oiof the diverting or stopping device has to be eifected in anextraordinarily short space of time. e. g. in 6 sec. This problem may besolved by a purely electrical switching device with two stable positionsoi' equilibrium, e. g. by the employment of electron-tubes, glow-lampsor spark gaps. The invention provides for this purpose a speciallysimple and rapidly reacting electron-tube device, which is actuatedsimultaneously with the start of the voltage to be recorded by theoscillograph. In this way the voltage of the grid-potential of anothervalve (the so-called deiiector tube) can at the same time be maintainedat the same value, and its saturation-current made to iiow to through acondenser connected in parallel with the controls, the voltage of whichis thus varied proportionally with the time.

With apparatus for picture-telegraphy or television, in which the wholearea of the picture both in transmitter and receiver is scanned by thefocal spot in a zig-zag path consisting of upward and downwardstraight-line branches, one set of branches. say the upward. can bedescribed at a constant relatively slow velocity, and the other set, thedownward, at a constant relatively high velocity by suitably varying thecontrol voltage, as by charging or discharging inserted condensers bymeans of a constant current, e. g. the saturation current ol.' electrontubes. This must be effected by employing two different constantintensities of current. Thus only the one set oi parallel branches isvalid for the chemical and physical effects, in contrast to thehitherto-used sinusoidal records. in which, on each of both branches,the recording velocity and the distance from the neighbouring branch arecontinually changing.

The cathode-ray oscillograph forming the subject o! this invention canbe used in picturetelegraphy and television also in the transmittingstation i'or scanning the picture to be transmitted, and further forfrequency-multiplication ior secret telegraphy and the like by scanningseparated electrodes arranged chess-boardwise behind the window andeasily exchangeable.

Since neither for transmission nor reception need any mechanical partsbe moved, the new cathode-ray oscillograph, especially forpicturetelegraphy and television offers a number of such importantadvantages as to enable both these operations to be carried out withhitherto unattainable perfection.

The synchonization which must be maintained between transmitting andreceiving apparatus, is obtained with the utmost ease and with absoluteexactitude by simultaneously aiecting the corresponding controls of thetransmitter and the receiver by the voltage either directly by wire, orindirectly by wireless waves.

'I'he advantages of a constant recording speed have already been pointedout above.

The recording velocity obtainable is so great that e. g. a picture of6x6 cm may easily be scanned in 1/1000 sec., or even in 1/10,000 sec.,and reproduced with suflicient intensity.

If a picture-frequency of not more than 16 pictures per second (which isadequate for the human eye) is required, pictures of such intensity maybe obtained, that they may be projected on a much enlarged scale on to ascreen and made Visible to a large company of spectators.

Picture-telegraphy can be extraordinarily cheapened and its field ofapplication extended beyond all anticipation.

For instance, the transmitting of a. picture, which hitherto requiredabout ten minutes, can be reduced to 1/1000 of a sec. An entirenewssheet, for instance, can be swiftly transmitted bypicture-telegraphy, provided only the sheets to be transmitted and thereceiving film are moved with sufficient velocity.

Cinematographic illms can be copied by wireless transmission at anydistance.

'I'he speed with which the pictures can be scanned in the transmitterand receiver makes it possible to scan, transmit, and reproduce in onecontinuous line pairs of stereoscopic pictures, so that either static orin process of production plastic picture-telegraphy and plastictelevision are made possible in the simplest manner by one and the sameapparatus.

The extraordinary speed with which a picture can be scanned at thetransmitting station and recorded at the reception station, and thepossibility oi' extremely rapid withdrawal of the focus after thepicture has been completely scanned, enable also the transmitting andreception devices to be used for super-speed recording of slow motionpictures, in which case a much greater number of pictures per second caneasily be recorded, than has been possible with slow motion apparatushitherto used.

If a very high number of pictures per second is to be obtained, it is,for instance, only necessary, rsty, in the receiving apparatus, todouble the length of the picture, that is to say the sum of theintervals between all the branches oi the zig-zag path, so that with astationary photographic plate one would obtain a distorted picturedouble the width; and secondly, to run the receiving iilm constantly athalf speed. 'I'his gives the slow motion pictures, the opticalcompensation otherwise required being here replaced by the swiftwithdrawal of the focus.

The invention is exemplied in the drawings.

Fig. 1 shows schematically a cathode-ray oscillograph, such as can beemployed for the various above mentioned purposes.

Fig. 2 shows on a larger scale-schematically drawnan example of thewindow of a cathoderay oscillograph used for the transmission ofpictures or for television.

Fig. 3 shows a window of the same lsort in the receiving apparatus, forthe photographic record of the wirelessly transmitted picture.

In Fig. 4 is schematically represented, how the cathode-ray tube of thetransmitter and the cathode-ray tube of the receiver work together inthe pictureltelegraphy or television.

Fig. 5 shows on a larger scale a vacuumproof pliable device for shiftingmovable parts, such as, e. g., a deiiector plate.

Fig. 6 is the schematic representation of a tube for auto-electronicdischarge with a cold cathode and supplied with electrostaticconcentrating device.

Fig. '7 represents a thermionic cathode-ray tube with an interceptingelectrode, the latter actuated by a tip-action electron-tube device.

Fig. 8 shows a connection scheme for the production of oscillations withlinear variations of voltage, as used especially for televisional orpicture-telegraphic apparatus.

Fig. 9 shows the wave-shape of the linear oscillations produced by meansof such a connection.

In the cathode-ray oscillograph represented in Fig. 1 the cathode-raybeam is produced in the metallic discharge-tube I,.which serves at thesame time as an anode, and into which the cathode 2 is introduced bymeans of the bushing 3. The cathode 2 is connected with the feed-voltageby means of the rod 3 lodged in the bushing 3. 'I'he coil 4 serves toconcentrate the ray beam before it passes through the narrow aperture ofthe diaphragm 5 in to the actual diversion-chamber 1 and onto theelectron-permeable window 6.

8, 8' are the deflector plates, which can be adjusted under a highvacuum with the help of elastic bodies 9 `or membranes I0 by means oiscrews II, which are lodged in supporting tubes I2. I5 is a spy-hole,through which the oscillogram to be recorded can be observed also whilethe photographic record is being taken, provided that the inner side ofthe electron-permeable layer 6 or parts of the grid 19 are overlaid witha phosphorescent substance. The photographic layer (plate or film I4) issituated during the taking of the record in the shutter I3.

Fig. 2 shows on an enlarged scale in sectlon an example of aphotoelectric-cell,arrangement for taking pictures. Close behind theelectronpermeable window 6, which is also held by the grid 19, issituated the photo-electric plate 8|, which is subdivided by means ofinsulation-layers into as many small fields as picture-stippling pointsare desired. The small photo-electric cathodes of the plate 8i are thensupplied successively with negative voltage by the electronic beampassing rapidly across them; the intensity of the current ilowing offover the common grid anode 92 and the amplier |06' (Fig. 4) is modiiedthen according to the resistance effective at any given moment dependenton the exposure of the cell in question. y

Instead of a photo-electric cell an exchangeable electrode arrangementof any desired formation can also be fixed on the recording apparatusbehind the electron-permeable window, enabling a definite succession ofcurrent impulses to be sent out for which the receiving apparatus mustbe arranged accordingly.

A simple method of transmitting pictures also consists in first copyingthe picture according to a certain process onto a metal plate in such amanner that denite conductivity-values at different points of thesurface of the metal plate correspond to the varying intensities oflight on different parts of the picture. The electronic beam passingthrough the electron-permeable window can excite directly fluctuationsof current in the ampliiier |06' (Fig. 4) which serve to vary theintensity of the cathode-ray in the receiver.

A further possible method of application of the invention topicture-telegraphy consists e. g. in utilizing the travelling point oflight produced outside the transmitter-tube on the uorescent screen overa system of lenses for scanning the picture to be transmitted and havingthe reected rays gathered up by one single large photo-electric cell.

Fig. 3 shows on an enlarged scale in section an example of theconstruction of an electronpermeable layer E for cathode-rayoscillographs with a. supporting grid 19 of metal strips placededgewise. The electronic beam when not in use falls behind one of thealuminium blades 83; the X-rays then generated are screened off by alead mantle 84. The oscillogram or picture appears on a uorescent layerfixed onto the exterior side of the electron-permeable foil 6. Ifphotographic records have to be made, the light-sensitive lm or plate I4is pressed closely onto the electronpermeable window 6 by means of thelightproof shutter I3.

Fig. 4 shows an example of an arrangement for a cathode-ray oscillographin accordance with the invention, applicable for picture-telegraphy andtelevision, a denoting the receiver arrangement, b the transmitterarrangement; both are, wireless transmission being pre-supposed,connected with each other by way of antennae 9|' and 9I. For sending andreceiving there serve respectively the cathode-ray oscillographs 92 and92 with hotcathode discharge devices 93' and 93 respectively, pairs ofdeflector-plates 94', 95', and 94, 95 and electron-permeable windows E'and 6. The pairs of deector plates 94', 95' and 94, 95 respectivelyshown in the diagram for the sake of clearness as parallel lie in theactual apparatus in each tube in planes at right angles to each other.'Ihe feed voltage for the discharge tubes lies at points 91', 98' and91, 98 respectively.

By means of intercepting-electrodes 99' and 99 respectively, arrangedbetween the hot-cathodes in the tubes 93 and 93 respectively and thecorresponding anode 91' and 91, the generation of electronic-rays duringthe pauses, and thereby the fusing of the window, is prevented. Theelectrons passing through the electron-permeable layer B' of thetransmitter tube 92 fall upon a photo-electric cell of specialconstruction |00, the photoelectrically active layer 8l of which isdivided in a manner known per se into a large number of small separateareas (shown enlarged in Fig. 2). On the photo-electric layer there isformed by means TIS of lenses |0| a picture of the'object |02 to bereproduced, so that there falls upon each of the areas a definite, ingeneral varying intensity of light. The illumination takes place throughthe wide-meshed grid 82, which serves as common anode for all the smallphoto-electric cells. The actual transmission is effected by means ofthe high-frequency transmitter |03, which is coupled directly with thetransmitting antenna 9 I and in turn modulated by the oscillator |04 and|05' as well as by the fluctuations of the photo-electric cells 8|conducted by way of amplifier |05'. Both oscillators |04 and |05produce. by means of a device known per se, represented in Fig. 8,oscillations with a time-proportional Voltage-variation of theWave-shape sketched in Fig. 9. In this manner there is ensured, incontrast to what happens in the case of the sinusoidal oscillationsfrequently used for such purposes, a precisely timeproportional scanningof the picture to be transmitted.

The transmission of a picture from the transmitter to the receiver takesplace in the following manner:

Oscillator |05' produces continuously oscillations of a definitefrequency, about 105 per sec., which affect the pair of plates 95' ofthe transmitter tube 92', and are transmitted by way of thehigh-frequency transmitter |03, the transmitting antenna 9|', thereceiving antenna 9| and the selective amplifier |05 to the pair ofplates 95 o'f the receiver tube 92. When oscillator |05 is aloneworking, the oscillations of the electronic beam describe a stationaryline equal to the height of the picture to be transmitted, both in thetransmitter tube and receiver tube.

If now the oscillator |04 is also switched on (frequency about 103 persec), which aects the second pair of deflector plates 94' standing atright angles to 95' of the transmitter tube, these oscillations aretransmitted by way of the same path as those from oscillator |05',through a selective amplifier I 04,to the pair of deectorplates 94 ofthe receiver tube 92, and the original line is once again transformedinto a progressive zigzag record. If the frequency of the oscillator|04' is properly adjusted, the record produced has the width of thepicture transmitted. If in addition the width of the oscillator I 05' isnot greater than about the Width of the line described by the focusspot, each point of the picture being transmitted, both in thetransmitter tube and in the receiver tube, is scanned simultaneously andfor an equal period by the cathode-ray beam.

The interception of the electronic beam when not being used is hereeffected by means of the intercepting electrodes 99 and 99' respectivelyby way of a--not here shown-tip-action electrontube device similar tothat represented in Fig. '1, which is controlled by means of theoscillator I 04 and theV amplifier |04. As the cathode ray beam on itsway through the transmitter tube 92' meets with varying degrees ofresistance according to theconductivity of the photo-electric cell withwhich it happens to be in contact, fluctuations of current take placecorresponding to the occurring differences of intensity. Thesefiuctuations are transmitted by way of the amplifier |06', the highfrequency transmitter |03', the transmitting antenna 9|', the receivingantenna 9|, and a selective amplifier |06, onto the control grid I1 ofthe receiver tube 92, there giving rise to corresponding fiuctuations ofthe beam-intensity, which in turn cause the requisite fiuctuations inintensity of the picture reproduced on the fluorescent screen 0.

'I'he arrangement schematically represented in Fig. 4-both thetransmitting and the reception apparatus-allows also in the simplestmanner possible of transmitting stereoscopic pictures to any distanceand likewise of stereoscopic television. If the windows 9' and 0 aremade so long in one direction, e. g. in a direction perpendicular to theplane of the drawings, that both stereoscopic pictures in thetransmitting apparatus can be scanned adjacently and adiacentlyreproduced in the receiver, then'both pictures are scanned by the focalspot in one continuous line in each of both apparatus. The stereoscopictransmission of pictures and stereoscopic television are thus realized.

In Fig. 5 is exemplified on a larger scale the pliable device shown inFig. 1 employed for shifting movable parts under a high vacuum. Thedevice here serves for the adjustment of the electrostaticdefiector-plate 8, by means of the pliable metal body 9 actuated by nut|01, pressing upon the carrier-bush 24. 'I'his is joined by means ofthree screws 25, sliding in slots of the jacket 26, with the guide-ring21, into which, by means of an insulating Washer 29,'e. g. of Bakelite,is fixed the supporting rod 28 of the deflector plate 9. The pliablebody 9 is joined in a vacuum-tight manner at both ends withv itsguide-rings, and likewise the insulating washer 29 with guide-ring 21;furthermore the supporting rod 29 is guided by another perforatedinsulating washer 30. The ring 3| carrying washer 30 is fixed directlyinto the jacket 'I of the cathode-ray tube. l

The tube 32 for auto-electronic discharge shown in Fig. 6 contains ananode 33 and an intercepting electrode (auxiliary anode) 34 which duringthe release of the beam functions as an anode. The release is effectedby two spark gaps or glow-lamps 35 and 36, connected by way of windings31. 39 with the perforated intercepting electrode 34 and by way of ahigh resistance element 39 with the cold cathode 40. The high-tensioncontinuous current required for feeding the tube is generated in theknown manner by means of transformer 4|, valve 42, and condenser 43. Ifthe gaps 35 and 36 are properly adjusted, any sudden surge of voltagearising from the transmission line orantenna 44 and inducted from thewinding 45 according to the polarity of the surge, either onto thewinding 31 or 38, causes a sparking of the gap 35 or 38, the duration ofwhich depends upon the value of the capacity 46 and the resistance 41.By this the electrode 34, which has hitherto intercepted the beam,becomes an anode, and the extremely sharp point of the cathode elects anelectronic beam through the perforations in the electrodes 34 and 33,the intensity of the beam can further be varied by means of thecontrolling electrode 33 by varying the angle of the cone-shapedelectronic beam.

In the lower part of Fig. 6 is shown schematically an electrostaticdevice for concentrating the electronic beam. It consists of cylindricalmetal tubes 49, sustained by supports 49 in such a position as to allowof the electronic beam passing freely through it, and of the metal ringwashers 50 between the tubes 48. If the washers 50 are chargednegatively to the tubes 48, divergent electric fields are formed, whichexercise a force concentrating radially the beam. Thus an exceptionallyminute focal spot is obtained.

The beam focusing arrangement described above and shown in the drawingsfor the sake of a complete disclosure is not claimed herein but formsthe subject matter of, and is claimed in the copending application'ofMax Knoll, Serial No. 5,136, filed February 5, 1935 for Cathode-rayoscillographs.

'I'he thermionic cathode-ray tube 5| shown in Fig. 7, is provided withhot cathode 52, anode 53 and ,control-grid 54 controlling the intensityof the electrons in the beam while the latter is working. In order toprevent the fusing of the window during periods when the focal spot isat rest, an intercepting electrode 55 is provided, actuated by atip-action electron-tube device. This device consists of theelectron-tubes 56, 51, and 58, the anodes of which are connected on theone hand by way of resistances 59 and 60 with the positive pole of astorage battery, and on the other hand crosswise by way of condensers6|, 62 with the grids of the tubes 56 and 51. By means of a battery 63,which by way of the high resistances 64, 65 keeps the condenser 6Icharged, the grid potential of the tube 56 is kept at a lower level thanthe anode potential of tube 51, the amount of the diminution being aboutthe same as the anode potential itself. If the grid of the tube 51 Whichis fully emitting during the interception of the cathode-ray beam, isaffected by a surge of negative voltage issuing from the antenna ortransmission-line 66 by way of the resistances 61 or 68, and by way ofthe condenser 69, the arrangement tips over into its other position ofstable equilibrium. In that case tube 51 is blocked. The grid potentialof tube 56 and therewith that of the intercepting electrode, hithertonegative, now receive the same potential as hot cathode 52, or apotential positive to it, and the cathode-ray beam is released. If thesurges issuing from the antenna or line 66 are positive, the tube 58acts in the same manner. By means of resistance 10, the time of thetipping-over of the device into the position of equilibriumcorresponding to the period of interception of the cathode-ray beam maybe adjusted at will, thus enabling the release to be maintained for anylength of time desired.

Fig. 8 refers to a device suitable for the production of oscillationswith linear variation of voltage, such as is provided for oscillators|04' and in Fig. 4. In Fig. 8, 1I and 1.I are triodevalves, fed by thebatteries 12 and 12. By the saturation-current of these valves` thecondenser 13 is alternately charged and discharged by way of theresistances 14 and 14. The charging and discharging is automaticallycontrolled by the grids 16 or 16', the potential of which is maintainedat a suitable level by means of batteries 15 and 15. By varying thecapacity of the condenser 13, the required frequency may easily andswiftly be obtained when working.

If the saturation-currents of the valves 1| and 1 I are selected atvarious values, or the resistances 14 and 14' are given differentresistivities, the upward branches 11 of the oscillations taking placeproportionally with the time (see Fig. 9) become less steep than thedownward branches 18, whereby both in the transmitter and in thereceiver the eilect of the downward branches is diminished in comparisonwith that of the upward branches.

If the batteries 15 and 15 shown in the conncctiomscheme Fig. 8 andtheir connections are omitted, the grid 15 joined with the hot cathodeof its tube, and the grid 16 affected by the voltage of a control of thecathode-ray oscillograph, e. g. by the Voltage of the oscillator 105'shown in Fig. 4, then a positive dependence is obtained of the controlvoltage |04' upon the Voltage of the control |05'. That is to say, thelengthwise return of the focal spot occurs always after a definitenumber of transverse oscillations.

We claim:

1. A cathode-ray oscillograph comprising, a bathode for producing a beamof electron-rays, a beam focusing member for bringing the rays to afocus, deflecting means to deflect the said focus sideways in lionedirection, another deilecting means to deect the said focus transverselyto the said direction, an electron-permeable window lying in thevicinity of the area in which the said focus is designed to move duringits deflection in the said two directions, and means to automaticallyprevent the rays from striking the said electron-permeable window whileone of the said focus deecting means is ineffective to maintain motionof the focus over the window.

2. A cathode-ray oscillograph according to claim 1, in combination withan adjusting means for the deilecting means within the vacuum,consisting in an elastic closure element supporting the deiiectingmeans.

3. A cathode-ray oscillograph according to claim 1, the said windowbeing supported by a grid in the form of a plate having a plurality ofsmall holes adapted to lie substantially in the focal spot of the beam.

4. A cathode-ray oscillograph according to claim 1, the said windowbeing supported by a grid, the said grid comprising flat metal stripsfixed edgewise against the window and forming with the window, at allpoints of contact with the window, diierent angles corresponding to theangles of. incidence of the electronic rays at said points of contact.

5. A cathode-ray oscillograph according to claim 1, the said windowbeing supported by a grid consisting of a thin foil deposited directlyon the outer surface of the said grid.

6. A cathode-ray oscillograph according to claim 1 in combination withelectrodes in front of the window and outside thereof.

7. A cathode-ray oscillograph according to claim 1 in combination with auorescent layer on the inside of the window.

8. A cathode-ray oscillograph according to claim 1, the said means toautomatically prevent the rays from striking the window comprises adevice for deiiecting the electron-rays by means of electrostatic forceswhile the focal spot is at rest.

9. A cathode-ray oscillograph according to claim 1, the said means toautomatically prevent the rays from striking the window comprising adevice for defiecting the electron-rays by means of magnetic forces.

10. A cathode-ray oscillograph comprising an electron-beam receivingmember, a cathode for producing a beam of electrons, means for bringingthe beam to a focus at the receiving member, beam deflecting meansoperable in response to electrical Variations to effect movement of thefocus of the beam over the receiving member. and means to automaticallyprevent the beam from striking the receiving member while the saiddeflecting means is ineffective to maintain motion of the focus,comprising means for deflecting the beam beyond one edge of thereceiving member, and a plate of material of low atomic weightjuxtaposed to the edge of the receiving member to receive the beam whenso deected.

11. A cathode-ray oscillograph comprising an electron-beam receivingmember, a cathode for producing a beam of electrons, means for bringingthe beam to a focus at the receiving member, beam deflecting meansoperable in response to electrical variations to effect movement of thefocus of the beam over the receiving member, and means to automaticallyprevent the beam from striking the receiving member while the saiddeecting means is ineffective to maintain motion of the focus,comprising means for deilecting the beam beyond one edge of thereceiving member, a plate of material of low atomic weight juxtaposed tothe edge of the receiving member to receive the beam when sol deected,and a screening mantle for said plate composed of material of highatomic weight.

12. A cathode-ray oscillograph comprising in combination, a cathode forproducing a beam of electron-rays, a beam focusing member for bringingthe rays to a focus, an electron beam receiving member lying in the pathof the beam, deecting means for moving the focus sidewaysuninterruptedly from side to side of the said receiving member, anotherdeecting means for moving the said focus transversely to the said onedirection uninterruptedly from end to end of the receiving memberwhereby the two deiecting means are capable of moving the focus oversubstantially the entire area of the receiving member, and means toautomatically prevent the rays from striking the receiving member whileone of said deilecting means is ineiective to maintain motion of thebeam over the receiving member.

13. A cathode-ray oscillograph as claimed in claim 12 in combinationwith a iluorescent layer on the inside of the electron beam receivingmember.

14. A cathode-ray oscillograph as claimed in claim 12 in which the saidmeans to automatically prevent the rays from striking the electron beamreceiving member comprises a device for deflecting the electron rays bymeans of electrostatic forces while the focal spot is at rest.

MAX KNOLL. LUDWIG SCHIFF. CARL STOERK.

I DISCLAIMER 2,036,532.-Ma Knoll, Berlin-Lichterfelde, Ludwig Schei,Berlin, and Carl Stoer/c,

Berln-Neukolln, Germany. CATHODE-RAY-OSCILLOGRAPH.

Patent dated April 7, 1936. Disclaimer filed February 13, 1939, by thepatentees.

Hereby disclaim claim 12 as it appears in the patent exce l pt as 1taiects clalm 14 which latter 1s appendant to clalm 12, and also d1sclaimfrom the patent claim 13.

[Oficial Gazette March 21, 1.939.]

